Description
Anaerobic digestion (AD) can generate energy from organic municipal solid waste, but existing wet-digestion methods used in wastewater treatment don’t suit high-solids waste like food scraps. High-solids AD is commercially applied but often not cost-effective, so technological improvements are needed.
This study focused on multi-stage AD systems, which separate hydrolysis and methanogenesis for higher energy yields but at higher costs. Researchers tested ways to improve hydrolysis, the limiting stage, using leach bed reactors. The challenge is that ammonia and salinity inhibit microbes during long-term operation. Experiments showed that using acclimated microbial inocula, especially combining solids-based and leachate-based inoculation, improves hydrolysis efficiency under high-inhibitor conditions.
Lab-scale tests confirmed the benefits of inoculation when inhibitor levels were high, while demo-scale tests showed little effect since inhibitors had not yet built up. Economically, the studied high-solids multi-stage AD system is competitive in capital costs with existing technologies, but profitability depends heavily on energy prices. Improving hydrolysis rates could reduce capital costs and shorten payback periods, making the technology more viable.
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